Bike Tail Light With Standlight （2）

Published:2011/8/2 22:18:00 Author:Phyllis From:SeekIC

By ralf Nolde

Construction

The circuit can be built on the single-sided circuit board. The PCB layout accepts conventional wire-ended components with some of them fitted to the underside (alternatively you can keep them all on the same side by fitting R5 over the top of D5/D6 and R6 under rectifier Bl).

The PCB is quite small but this should not pose any problems when mounting the components. It is important to double check that all polarised components (diodes, transistors and electrolytic capacitors) are fitted the correct way round before power is applied to the circuit.

A 9 V battery or mains unit can be used to test the unit. The power source is connected in place of the dynamo, polarity is not important because the bridge rectifier ensures that power will always be correctly supplied to the circuit. At power-up all the LEDs should light and after a short charging time the voltage across the Goldcap can be measured (approximately 5.5 V) while the voltage drop across R4 should be less than 0.75 V.

Once the circuit has been tested, mask off the LEDs with tape and give the whole unit a few coats of spray lacquer to protect it from the effects of the weather. Once the lacquer is dry the unit can be mounted in the taillight housing. The PCB is dimensioned to fit in a housing type 339 made by the company Busche & Miiller and distributed on the UK by Amba Marketing. It can also be adapted to fit into any similar rear light housing.

For the housing specified, the PCB is fitted behind the reflector part and fixed with a small (rust proof) self-tapping screw. Cycles are subject to surprisingly high levels of shock and vibration so it is a wise precaution to support all the major components like capacitors transistors and LEDs with an application of hot-melt glue after the circuit has been fitted and wired to the dynamo. Lastly fit the rear light lens and ensure that the LED is correctly aligned with the reflector lens opening.




UK laws at a standstill?

In the UK lights on a bicycle are not required when stationary and to comply with the law the lamp should have a filament! British Standards have been updated to allow LED light sources and these have been commonly in use for a number of years but to be legal the lamp should have a filament. So a lamp with a BS approval could be illegal. The law is seldom if ever enforced on this point and rightly so because it’s safety that matters. Cyclist also uses flashing lights even though they are also technically illegal. Surveys indicate that most cyclists (about 90%) use battery powered lights.

The two documents concerning cycle lighting are the 1989 Road Vehicle Lighting Regulations and British Standard 6102 part 3. Any form of home-made lighting will not have BS approval. The Bike Tail Light described in this article should only be used as a secondary means of lighting which is fitted together with a BS approved system.

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